Generally, digital video cameras and digital cameras have CMOS-type imaging devices or CCD-type imaging devices mounted thereon. For example, a CMOS type imaging device has a sensor chip which converts an image of a subject into electrical signals, a signal processing chip which processes signals output from the sensor chip, or the like. The sensor chip and the signal processing chip are coupled to each other by wire bonding or the like.
The sensor chip has, for example, a pixel array in which a plurality of pixels is arranged in a 2-dimensional matrix and sequentially outputs analog electrical signals generated by each pixel to the signal processing chip. The signal processing chip has, for example, an A/D converter and sequentially converts the analog signals received from the sensor chip into digital signals.
In recent years, imaging devices having the function of a signal processing chip such as an A/D converter provided within a sensor chip have been proposed (see Patent Document 1, for example). A sensor chip of this type has, for example, an A/D converter in each column of the pixel array. Accordingly, it is possible to speed up A/D conversion processing in comparison with the above-mentioned prior art which outputs the analog pixel signals output from the pixel array to the signal processing chip in a serial form, and which converts them into digital data.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008-48313